Symbiosis – from organisms to Earth

1. Symbiosis – from organisms to Earth KAUST – Winter Enrichment Program 31 January 2011 John Cheeseman University of Illinois, USA http://www.life.illinois.edu/cheeseman/KAUST/symbiosis.ppt

2. All organisms on earth occur in some sort of symbiotic relationship with other organisms. • Symbiosis was probably critical for the colonization of land by multicellular organisms. • Symbiosis affects all parts of our lives… • plant growth, productivity and survival • human pathogens and diseases • biogeochemical cycling • functioning of the planet itself Today - we will look at symbiosis at all levels, however briefly, with particular emphasis on some of the consequences of disrupting it at the planetary scale.  Some implications for the future of humans on earth will also be discussed.

3. Land colonization began ca 1.2 Ga with cyanobacterial mats • Fungi added (lichens) ca. 600 Ma There are >13000 spp of lichen fungi… ~20% of all known fungi

4. Plants arose ca. 500 Ma - no leaves or roots • Earliest fossils have fungal associations • Why? So what? • Today, the most well-known mutualistic plant/fungal association is mycorrhizae… • involves >80% of all plant species… • critical to P, Zn and K nutrition • especially in poor soils Aglaophyton - ca 420 Ma

5. Plants also associate with bacteria • Bacterial N-fixation is agronomically and ecologically critical Frankia nodules on alder Rhizobium on soybean Bacteroids in Rhizobium nodules

6. Nodulation and mycorrhizae formation share signalling pathways Following Nod or Myc factor signaling, a nuclear calcium/calmodulin dependent kinase is activated which phosphorylates transcription factors needed for nodule differentiation or AM development.

7. Single legume roots may be infected with both VA mycorrhizae and Rhizobium

8. Spartina dominates East Coast, US salt marshes characterized by oligotrophic conditions Symbiosis is not limited to nodules and mycorrhizae … plants still provide C to the symbionts (as much as 40% of total photosynthate) Rhizoplane bacteria

9. Chemotaxis of Zoöspores

10. Other interesting symbioses – some examples • Epichlöe – a fungal endosymbiont transmitted in seeds • Protects its grass host from grazers – bad for grazing, great for turf grass • Confers stress tolerance

11. Other interesting symbioses – some examples • Photosynthetic sea slugs and sea anemones • Corals • Bioluminscent squid and angler fish • Gut symbionts (ruminants, monkeys, termites, people) • Leeches, tsetse flies, lice, bed bugs, mites… can live on your blood because endosymbionts synthesize B vitamins and other nutritional supplements

12. Endosymbionts of termites Symbiotic archaeoprotist from the intestine of the termite Reticulitermes flavipes. … Trichonympha agilis … Pyrsonympha verteus … Dinenympha gracilis. Symbionts eat the wood eaten by the termites, and their bacterial symbionts do the actual digestion. From Joseph Leidy (1881) - “The parasites of termites”

13. Dichanthelium lanuginosum (hot springs panic grass) • Yellowstone and Lassen Volcanic National Parks, US • Found on edges of hot springs, adjacent to thermal streams, and on fumaroles (steam vents) • One of most thermotolerant vascular plants: rhizosphere temperatures range from 20˚C - 57˚C

14. Seasonal records show soil temps > 45-55˚C for prolonged periods

15. The problem: Grown in a greenhouse or other controlled condition, Dicanthelium is not tolerant above 40˚C

16. Culturing leaves and roots reveals numerous fungal associations Curvularia protuberata on leaf and root of D. lanuginosum Curvularia asci The problem remains: Grown in controlled cultures, Curvularia is also not tolerant above 40˚C

17. An even more interesting problem: Cultured together, the pair is tolerant of 60˚C • Curvularia is not the only fungus that does this… Fusarium culmorum confers salt tolerance on dune grasses, watermelon and other plants… different strains dominate in different microhabitats. And… it is not just the plant fungal interaction: The fungus is infected with a virus that is required for the heat tolerance

18. Break

19. An ecosystem is …

20. An ecosystem is all the organisms living in a community as well as all the abiotic factors with which they interact. Many ecologists regard the entire biosphere as a global ecosystem…

21. Sustainability/stability of any ecosystem depends on biogeochemical cycles

22. Ecosystems are ruled by energy flows and chemical cycling What is heat?

23. In a compost heap, respiratory heat released by detritivores and decomposers leads to high, but optimal internal temperatures. Temperature rises because heat energy is transferred to water.

24. Ecosystems are ruled by energy flows and chemical cycling What is the role of detritivores? What happens if detritus is removed? What limits primary production?

25. Physical and chemical factors limit primary production in ecosystems • Productivity is the product of productivity per unit area, and total area • Most highly productive ecosystems are small in total area

26. Regional annual net primary productivity is spatially variable

27. Sustainability/stability of any ecosystem depends on biogeochemical cycles • Generalized scheme • Rate variations between systems largely reflect decomposition rates • Affected by temperature and water

28. Nutrient cycles are global Nitrogen fertilizer applied to Illinois corn is consumed and excreted in European feedlots, or re-exported as meat products

29. An more detailed example: the water cycle Is this “local” or “global”? How does this relate to symbiosis?

30. Global climate changes affects huge areas and billions of people though the biogeochemical water cycle Amazonian drought in 2005/6 fueled massive fires Coincided with very active North Atlantic hurricane season Effects of conversion of forests to savannah will affect even more people.

31. Atmospheric and ocean circulations result in massive redistribution of energy and matter

32. More on the water cycle • The water and sulfur cycles are linked: • Oceanic cloud formation & rainfall requires nucleating effects of biogenic dimethylsulfide • Pelagic birds may use DMS to find prey

33. Earth is characterized by unexpected stabilities Atmospheric composition varies very little over very long periods Hyperreactive gases such as O2, O3 and CH4 exist at relatively stable levels Ocean salinity varies little even though ocean makeup is far from equilibrium: river salt inputs should raise SW well above 3.4% salinity as should ocean circulation through hot basaltic vents CO2 cycle involves release from volcanoes, dissolution in ocean waters and precipitation in limestone both bioactively and inorganically… but changes are (were) slow over long periods.

34. On Earth, temperature changes are generally gradual and (even today) means are relatively stable

35. On Earth, temperature changes are generally gradual and (even today) means are relatively stable January 2010 Global Temperature Update

36. Most important environmental considerations at any scale are stability, and the magnitude and predictability of variation. • Oceans and atmosphere moderate variability • Year to year variations are small and long term changes are gradual • By contrast, on Mars… • No oceans and a thin atmosphere • Low thermal inertia • Climate easily perturbed by external influences, including solar variations • Mean temperature can change by many degrees from year to year, depending on how active large scale dust storms are

37. Martian climate is particularly sensitive to the strength and duration of hemispheric dust storms

38. Within an ecosystem, the linkages are not always obvious • Three ecosystem components • Biosphere • Lithosphere • Atmosphere • … interact unpredictably

39. Within an ecosystem, the linkages are not always obvious Salpa aspera – the missing link for CO2 ? One swarm covered 38,600 square miles (100,000 square kilometers) of the sea surface… perhaps trillions of thumb-sized salps…. Consumed up to 74 percent of surface microalgae per day… their sinking fecal pellets transported up to 4,000 tons of carbon a day to deep water.

40. Gaia … a planetary physiological system that regulates the chemistry and climate … atmospheric homeostasis controlled by and for the biosphere … Earth is a single living organism … a symbiotic planet. "It is remarkable how exact the balance is between the carbon input from volcanoes and the output from rock weathering…; This suggests a natural thermostat which helps maintain climate stability." James Lovelock

41. Lynn Margulis Gaia can be viewed not as an organism but as an emergent property of a complex system, reflecting interaction among organisms • Complex systems show non-linear behavior full of unknown unknowns. • Small changes have profound consequences • “Tipping points”

42. Homeostasis, homeorhesis and emergent properties Population as an example of emergent properties in complex systems

43. Break

44. “An ecosystem is all the organisms living in a community as well as all the abiotic factors with which they interact.” All aspects of the global ecosystem are dominated by a single organism - humans. • Our population is growing • At 6.66.75 6.89 billion (45/km2) • Up > 35% since 1988 • Up > 260% since 1950

45. There are no pristine environments. There is nowhere spared from human domination.

46. 6 trillion plastic bags per year try as I might I cannot conceive cannot fathom in my wildest imagination 16,438,356,164 per day 684,931,506 per hour 11,415,525 per minute 190,258 per second, for each beat of my heart as I rest in bed at dawn 9513 in the blink of an eye or a single frame in a moving picture 882 for each living, breathing human soul on the planet 163 for every acre of land 2.3 for each corn plant in the US 15 for every tree 43,011 per square mile of ocean 101,694,915 for each species of mammal 20,689,655 for each species of plant 1.5 billion for each species of cockroach 200 million for each sea turtle waiting to eat a jellyfish

47. A known known - Environmental change is brought about by “forcing agents” • Forcing agents include: • CO2 (up 40% since 1750) • Aerosols • CH4 (up 150%) • NOx and other greenhouse gases • Orbital variations • Solar output

48. A known known - Environmental change is brought about by “forcing agents” • Forcing effects are manifest as changes in the solar constant • Small changes are important • Since 1750, the effective solar constant has increased ca. 1.5 W/m2 (ca. 0.1%)

49. A known known - Environmental change is brought about by “forcing agents” 75% of change due to fossil fuel burning 25% due to land use changes (especially deforestation) Annual imbalance is only 2-4 GT/yr Emission are still rapidly rising In 1990s – 1.3%/yr. Since 2000 – 3.3%/yr

50. Environmental change is brought about by “forcing agents” Graph shows “anthropogenic global warming”